Can anyone explain why, after I’ve filmed a subject against a green screen and then chroma-keyed it onto a video background, the edges of the inserted subject becomes blurred and, in general, the subject itself loses its original sharpness?
No matter how much I adjust the chroma-keyer controls (Colour Tolerance, Saturation Minimum, Softness, Spill Suppression) the chroma-keyed subject remains blurred, not least around the edges.
In short, why does the quality of the inserted image become compromised in this way?
Ian Woodward
Green screen and chroma keying
Re: Green screen and chroma keying
IanIan Woodward wrote:Can anyone explain why, after I’ve filmed a subject against a green screen and then chroma-keyed it onto a video background, the edges of the inserted subject becomes blurred and, in general, the subject itself loses its original sharpness?
No matter how much I adjust the chroma-keyer controls (Colour Tolerance, Saturation Minimum, Softness, Spill Suppression) the chroma-keyed subject remains blurred, not least around the edges.
In short, why does the quality of the inserted image become compromised in this way?
Ian Woodward
There are many reasons why your '... your image quality may be compromised'
To help enable a better quality 'Key', the screen (green) should be well/evenly lit.
Your 'talent' should be placed as far as possible in front of the screen (2 mts or more).
Talent should then be properly lit.
Then it is down to the camera you are using. More specifically the sensor size, resolution,
dynamic range, etc.
In short, you will struggle with the average consumer model camcorder, to get a good Key.
It is not impossible to achieve 'reasonable' results by concentrating on the way you light
your screen and the 'placement' of the subject/s.
Kind regards,
Fred D
"Films are never released, they escape !" Ben Burtt
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Ian Woodward
- Posts: 133
- Joined: Thu Jan 07, 2010 2:24 pm
Re: Green screen and chroma keying
Thanks, Fred.
Apart from two softbox studio lights (500W each) on either side of the green screen, the subjects (situated about 4ft in front of the screen) are lit from each side, with a 300W light on the RH side being high looking down, a 300W light on the LH side being low down looking up. I used to light the subjects at an equal height, L and R, but this had a tendency to give flat lighting, with few shadows to give definition.
If I position the talent I'm filming further away than 4 or 5 feet from the 3m (L) x 2m (H) green screen, the talent's head appears above the height of the green screen in the camea viewfinder; an adult sitting down, or a child, is a different matter.
Close-ups, using the screen, are of a much better quality than head-to-foot shots in terms of the edges being cleaner, and of course it's no mystery why this should be so. It's just a pity that I can't get that cleaner look when filling, say, two or three people in long shot.
Ian Woodward
Apart from two softbox studio lights (500W each) on either side of the green screen, the subjects (situated about 4ft in front of the screen) are lit from each side, with a 300W light on the RH side being high looking down, a 300W light on the LH side being low down looking up. I used to light the subjects at an equal height, L and R, but this had a tendency to give flat lighting, with few shadows to give definition.
If I position the talent I'm filming further away than 4 or 5 feet from the 3m (L) x 2m (H) green screen, the talent's head appears above the height of the green screen in the camea viewfinder; an adult sitting down, or a child, is a different matter.
Close-ups, using the screen, are of a much better quality than head-to-foot shots in terms of the edges being cleaner, and of course it's no mystery why this should be so. It's just a pity that I can't get that cleaner look when filling, say, two or three people in long shot.
Ian Woodward